chapter 14 - reconstructing and using phylogenies Flashcards
define phylogeny
the evolutionary history of relationships among organisms or their genes
how are phylogenies demonstrated?
phylogenetic tree diagrams
each node (split) of the tree represents:
a divergence of lineages
T or F: rotation at the nodes and therefore the vertical order of the lineages are arbitrary
true
define the tree of life
the unifying concept of biology - all life is connected through evolutionary history
define convergent evolution:
independently evolved traits subject to similar selection pressures and may become superficially similar
two separate species may develop the same traits even though their common ancestor did not have it
define homoplasies (homoplastic traits)
similar traits that are generated by convergent evolution and evolutionary reversals
define evolutionary reversal
when a trait returns from a more advanced character to a more primitive one
define homologs
features shared by 2+ species that were inherited from a common ancestor
define homologs
features shared by 2+ species that were inherited from a common ancestor
define ancestral vs derived characteristics
ancestral: characteristic of a homologous trait that was present in the ancestor of the group
derived: a trait found in a descendent that was not present in the ancestor
define synamorphies
derived characteristics shared among a group that are viewed as evidence of common ancestry of the group
define ingroup vs outgroup when constructing phylogenetic trees
ingroup: the group of primary interest
outgroup: closely related species/group known to be phylogenetically outside the group of interest
what is the parsimony principle?
the theory that the simplest explanation of observed data for a phylogeny is the preferred explanation
minimizes the # of evolutionary changes that must be assumed (fewest homoplasies)
define Occam’s razor
the best explanation fits the data with the fewest assumptions
what kind of traits are used to construct phylogenies? (5)
morphological, fossil, developmental, molecular, behavioral, etc.
define a taxon
any group of organisms that is treated as a unit
ex. a genus, or all insects
what is the pattern of taxonomic classification?
domain –> kingdom –> phyla –> classes –> orders –> families –> genera –> species
define a monophyletic taxon
1 taxon contains an ancestor and all descendants of that ancestor, and no other organisms
the clade can be removed from the tree with a single “cut”
define a clade
a group of organisms believed to have evolved from a common ancestor
a taxon is a clade
define paraphyletic taxonomy
a group that does not include all descendants of a common ancestor
define a polyphyletic taxon
a group that does not include its common ancestor
what is the molecular clock hypothesis?
rates of molecular change are constant enough to predict the timing of evolutionary divergence
how to calibrate a molecular clock?
uses the average rate at which a given gene/protein accumulates changes to gauge the timing of divergences
